THE ROLE OF CHEMICAL, PHYSICAL, OR VIRAL EXPOSURES AND HEALTH FACTORSIN NEUROCARCINOGENESIS - IMPLICATIONS FOR EPIDEMIOLOGIC STUDIES OF BRAIN-TUMORS

This review highlights some future prospects and implications for epid emiologic research on the etiology of nervous system tumors. It review s some points regarding physiology of the nervous system, in connectio n with mechanisms of neurocarcinogenesis, and experimental studies in animals. The results of epidemiologic studies are summarized in the li ght of the biological and experimental observations. The following asp ects are particularly emphasized: (i) higher susceptibility of the dev eloping nervous system to neurocarcinogenic agents (in the fetus and a fter birth); (ii) possible implications of knowledge about mechanisms of neurocarcinogenesis regarding crossing of the blood-brain barrier, activation of oncogenes and inactivation of anti-oncogenes, relationsh ip between chemical structure and neurocarcinogenic action; (iii) nece ssity of further investigation concerning the occurrence of nitrosoure as and their precursors in the environment, and the potential role of nitroso compounds in the development of human brain tumors; (iv) lack of information about promoting or inhibiting neurocarcinogenic effects , and co-carcinogenesis-among others, interaction between X-irradiatio n and exposure to neurocarcinogenic nitrosoureas; (v) need for studyin g the potential neurocarcinogenic risk of polyomaviruses BKV, JCV, and SV40 to humans.